1. Field of the Invention
This invention relates to a laminated film, and more particularly to a laminated film, having as the core support member a polyethylene terephthalate film.
Polymeric films have found wide spread use in various applications including film base for photographic and magnetic recording members and also in the preparation of packaging materials. For photographic applications, cellulose acetate has become the most wide spread and preferred film base because its overall properties provide the optimum or close-to-optimum characteristics under the widest circumstance of use for photographic applications. A disadvantage of cellulose type film base is that in the preparation thereof, solvent coating applications are required which have been alleged to be harmful to the atmosphere and to humans.
In the applications for polymeric film set forth above, polyethylene terephthalate film has found an appreciable amount of use. However, polyethylene terephthalate film in some applications in the photographic industry is not suitable. A serious disadvantage with regard to polyethylene terephthalate film is that it is so tough i.e., its modulus is so high, that in the preparation of the film, particularly in the cutting operations, serious knife wear is caused, resulting in shut downs of the equipment in order to renew the knife edges. Also, in the preparation of motion picture film, the indexing holes which engage the sprockets in cameras and projectors, are formed by a punching operation. These punches are also rapidly worn because of the nature of the PET film. Not only is the wear of the knife edges utilized in the slitting operation and the wear of the punches for the formation of the indexing holes a problem but much debris is formed which interferes with the quality of the film when these cutting surfaces are dulled by continuous use. Still another problem with regard to the use of PET film base for motion picture films is that the toughness of the film prevents the film from breaking under certain conditions where film breaking is preferable to damage resulting to the components of the projector. It is preferred that the film break rather than the projector be damaged because of the cost involved in repair and also the time that the repair takes. Therefore, it would be an advantage to have a film base whose properties more approximate those of cellulose triacetate.
U.S. Pat. No. 2,901,466 issued to C. J. Kibler, A. Bell, and J. G. Smith on Aug. 25, 1959 and assigned to the same assignee as the immediate application discloses polyesters of 1,4-cyclohexanedimethanol and terephthalic acid for use in the preparation of films, fibers and other products wherein the products have improved dyeing qualities which permit dyeing to deep shades without the use of a carrier which is normal in the dyeing of polyethylene terephthalate.
U.S. Pat. No. 3,651,172 issued to K. T. Barkey and L. I. Laird on Mar. 21, 1972, and assigned to same the assignee as this application discloses linear block copolyesters of blends of poly(ethylenephthalate) with a random copolyphthalate of ethylene glycol and 1,4-cyclohexanedimethanol where the latter is present in an amount from 8 to 34 weight percent. Also disclosed is a laminated film having a polyethylene terephthalate film base which is laminated on one or both sides with the block copolyester described above.